Display controller architecture for portable computers

ABSTRACT

A dual display mode portable computer is disclosed. The portable computer includes a flat-panel display, and a display controller for outputting an internal video signal to the flat panel display. The portable computer further includes means for receiving an external video signal, and a multiplexer for outputting the internal video signal to the flat-panel display during a first display mode, and for outputting the external video signal to the flat-panel display during a second display mode, thereby enabling the portable computer to act as a display device for an external computer.

FIELD OF THE INVENTION

[0001] The present invention relates to portable computers, and moreparticularly to a display controller architecture for portablecomputers,

BACKGROUND OF THE INVENTION

[0002] Laptops and notebooks are names for portable computers that havea flat screen and usually weigh less than eight pounds. Most portablecomputers have connectors for an external monitor and keyboard fortransforming them into desktop computers.

[0003]FIG. 1 is a block diagram illustrating current display technologyfound in portable computers. Like most computer systems, a portablecomputer 10 includes internal hardware and software 12 for operating thesystem, and a display controller 14 for outputting an internal videosignal 16 to a flat panel display 18. The portable computer 10 alsoincludes a digital-to-analog converter 20 and an external CRT connector22 for outputting the video signal 16 to an external monitor, such as acathode ray tube (CRT) (not shown). With this type of displayarchitecture, the portable computer 10 is capable of outputting itsvideo signal on the flat-panel display 18, on the external CRT, or onboth the flat-panel display 18 and the external CRT at the same time.

[0004] The flat-panel display 18 tends to be one of the most expensivecomponents of the portable computer 10. Yet, today many portables 10become obsolete because various components, such as the processor,deliver lackluster performance relative to new computer systems.Therefore, it would be desirable to continue using the flat-paneldisplay 18 even after that portable computer 10 has become obsolete,perhaps as the monitor of a desktop PC (assuming the desktop PC has adual display adapter card). The problem is that today's portablecomputers 10 can only output video signals, but cannot receive videosignals from an external source for display on the flat-panel 18.

[0005] Accordingly, what is needed is a display controller architecturefor portable computers that allows portable computers to displayexternal video signals. The present invention addresses such a need.

SUMMARY OF INVENTION

[0006] The present invention provides a dual display mode portablecomputer. The portable computer includes a flat-panel display, and adisplay controller for outputting an internal video signal to the flatpanel display. The portable computer further includes means forreceiving an external video signal, and a multiplexer for outputting theinternal video signal to the flat-panel display during a first displaymode, and for outputting the external video signal to the flat-paneldisplay during a second display mode, thereby enabling the portablecomputer to act as a display device for an external computer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a block diagram illustrating current display technologyfound in portable computers.

[0008]FIG. 2 is a block diagram illustrating the display controllerarchitecture in accordance with one embodiment of the present invention.

[0009]FIG. 3 is a block diagram illustrating a display controllerarchitecture in accordance with a second preferred embodiment of thepresent invention.

DETAILED DESCRIPTION

[0010] The present invention relates to display controller architecturefor portable computers. The following description is presented to enableone of ordinary skill in the art to make and use the invention and isprovided in the context of a patent application and its requirements.Various modifications to the preferred embodiments and the genericprinciples and features described herein will be readily apparent tothose skilled in the art. Thus, the present invention is not intended tobe limited to the embodiments shown but is to be accorded the widestscope consistent with the principles and features described herein.

[0011] The present invention provides a display architecture forportable computers that allows portable computers to receive and displaythe output of a desktop PC or another portable computer.

[0012]FIG. 2 is a block diagram illustrating the display controllerarchitecture in accordance with one embodiment of the present invention,where like components from FIG. 1 have like reference numerals.According to the present invention, the portable computer 30 is providedwith an extended mode display (XMD) that enables the portable computer30 to operate dual display modes. In normal display mode, the portalcomputer 30 displays the internal video signal 16 on the flat-paneldisplay 18, while in XMD mode, the portable computer 30 receives anddisplays an external video signal 32 on the flat-panel display 18.

[0013] In the first embodiment of the present invention, the displaycontroller architecture includes a dual mode display connector 34, asensor 36, an analog-to-digital (A/D) converter 38, converter logic 40,and a multiplexer 42. In a preferred embodiment, the dual mode displayconnector 34 is a 15-pin RGB connector for coupling a video cable froman external PC or portable to the portable computer 30. The externalvideo signal 32 preferably comprises RGB analog input and timingsignals.

[0014] When the external video signal 32 is received on the connector34, the A/D converter 38 converts the signal 32 into a digital signal.The converter logic 40 then maps the output of the A/D converter 38 intoa format required by the flat panel display 18. After the conversion,the formatted digital video signal is input into the multiplexer 42. Themultiplexer 42 has two inputs: the standard internal video signal 16from the display controller 14, and the external video signal 32 outputfrom converter logic 40. The multiplexer 42 outputs either the internalvideo signal 16 or the external video signal 32 to the flat-paneldisplay 18 depending on the current display mode of the portablecomputer 30.

[0015] In a preferred embodiment, controls are added to the portablecomputer BIOS that would enable the portable computer 30 to operate inthe following modes:

[0016] 1) normal display mode—flat-panel only,

[0017] 2) normal display mode—flat-panel and an external CRT (same imageon both displays),

[0018] 3) normal display mode—external CRT only, and

[0019] 4) XMD mode

[0020] external signal displayed on external CRT and flat-panel.

[0021] In a preferred embodiment of the present invention, the displaymodes of the portable computer can be controlled in a variety of waysincluding automatic detection or by an explicit user command. Theautomatic mode requires the sensor 36 to automatically detect anexternal device coupled to the dual mode display connector 34 anddriving the external video signal 32 through the connector 32 when theportable computer 30 is powered-on. This can be an extension of thepower-on sequence of the portable computer 30. Alternatively, if theportable computer 30 and the external computer are already powered-onand the two are connected, it is possible for both computers to detecteach other. In this case, the user may be given an option to select a“hot plug” mode. In any event, once the sensor 36 detects the externalvideo signal 32, the portable computer 30 may be switched to XMD mode.

[0022] The second method for controlling the display modes of theportable computer 30 is through the use of a dual mode display softwaredriver 34 that enable the user to manually invoke the XMD mode either byclicking on an icon or by a key sequence. In a preferred embodiment, thedual mode display driver 34 displays a dialog box at startup that allowsthe user to select automatic switching mode or manual switching mode.The driver may also give the user an option to select the resolution ofthe external computer (e.g., VGA, XVGA, or SVGA) when it cannotautomatically be detected.

[0023] The manual method for switching the display mode is preferableover the automatic detection method because the user can toggle thedisplay between the primary flat-panel display 18 and the external PC.More specifically, the portable computer 30 remains on and fully bootedeven when the flat-panel 18 is used as the second display device of theexternal PC, and a hot key sequence is used to toggle flat-panel display18.

[0024] Once the display mode of the portable computer 30 is set, acontrol signal 36 is sent to the multiplexer 42 to control which videosignal is sent to the flat-panel display 18. If the portable computer 30is in normal display mode, then the multiplexer 14 outputs the internalvideo signal 16 to the flat-panel display 18. If, however, the portablecomputer 30 is in the XMD mode, the multiplexer 42 outputs the externalvideo signal 32 to the flat-panel display 18. A primary advantage ofusing the multiplexer-based display architecture is that multiplexer 42eliminates the need for a custom graphics controller, and the displayarchitecture can be implemented into current portable computer designs.

[0025] Referring now to FIG. 3, a display controller architecture isshown according to a second preferred embodiment of the presentinvention, where like components from FIGS. 1 and 2 have like referencenumerals. The second embodiment adds a dual mode display connector 52 tothe existing external CRT connector 22 of the portable computer 50 thatconnects to the external CRT connector 22, rather than adding a newconnector to the portable computer. The CRT connector 22 is a femaletype connector. Therefore, the dual mode display connector 52 is afemale to male type connector for accepting a display cord from anothercomputer. The advantage of using the dual mode display connector 52 isthat current portable computers do not have to be redesigned to accept anew input connector.

[0026] According to the second embodiment, a second multiplexer 54 isconnected between the external CRT connector 22 and the D/A converter20. In normal display mode, the D/A converter 20 outputs the internalvideo signal that drives an external CRT to the external CRT connector22. In XMD mode, a control signal 56 is sent to the second multiplexer54 to isolate the D/A converter 20 and to allow the external videosignal 32 to enter the external CRT connector 22 through the dual modedisplay connector 52. The external video signal 32 is then input to theA/D converter 38 and converter logic 40, and output to the flat-paneldisplay 18 through the multiplexer 42, as described above.

[0027] A display architecture that provides portable computers with anextended mode display has been described. The present invention has beendescribed in accordance with the embodiments shown, and one of ordinaryskill in the art will readily recognize that there could be variationsto the embodiments, and any variations would be within the spirit andscope of the present invention. Accordingly, many modifications may bemade by one of ordinary skill in the art without departing from thespirit and scope of the appended claims.

What is claimed is:
 1. A portable computer comprising: a flat-paneldisplay; a display controller for outputting an internal video signal tothe flat panel display; means for receiving an external video signal;and a multiplexer for outputting either the internal video signal or theexternal video signal to the flat-panel display.
 2. The portablecomputer of claim 1 further including an analog-to-digital converter andconverter logic coupled between the receiving means and the multiplexerfor converting the external video signal into a format required by theflat-panel display.
 3. The portable computer of claim 2 wherein thereceiving means includes a sensor for automatically sensing the externalvideo signal and causing the multiplexer to output the external videosignal for display.
 4. The portable computer of claim 3 whereinreceiving means includes a software driver that enables a user tomanually select between displaying the internal video signal or theexternal video signal.
 5. The portable computer of claim 4 wherein thereceiving means includes a dual mode display connector coupled to theanalog-to-digital converter for receiving the external video signal. 6.The portable computer of claim 4 wherein the portable computer includesan external CRT connector and wherein the receiving means includes adual mode display adapter coupled to the external CRT connector foraccepting the external video signal.
 7. The portable computer of claim 6wherein the portable computer further includes a second multiplexercoupled between the external CRT connector and adigital-analog-converter for isolating the output of thedigital-analog-converter so that the external video signal may bereceived through the dual mode display adapter and the external CRTconnector.
 8. A method for enabling a portable computer to display anexternal video signal, the portable computer having a flat-paneldisplay, the method comprising the steps of:
 1. providing the portablecomputer with means for receiving the external video signal; 2.inputting an internal video signal to a multiplexer;
 3. inputting theexternal video signal to the multiplexer; and
 4. providing the portablecomputers with dual display modes, such that in a first display mode,the multiplexer outputs the internal video signal to the flat-paneldisplay, while in a second display mode, the multiplexer outputs theexternal video signal to the flat-panel display, thereby enabling theportable computer to act as a display device for an external computer.9. The method of claim 8 wherein step (a) further includes the step of:coupling an analog-to-digital converter and converter logic between thereceiving means and the multiplexer for converting the external videosignal into a format required by the flat-panel display.
 10. The methodof claim 9 wherein step (a) further includes the step of: providing thereceiving means with a sensor for automatically sensing the externalvideo signal and causing the multiplexer to output the external videosignal for display.
 11. The method of claim 10 wherein step (a) furtherincludes the step of: providing the receiving means with a softwaredriver enables a user to manually select between displaying the internalvideo signal or the external video signal.
 12. The method of claim 11wherein step (a) further includes the step of: coupling a dual modedisplay connector to the analog-to-digital converter for receiving theexternal video signal.
 13. The method of claim 11 wherein the portablecomputer includes an external CRT connector and wherein step (a) furtherincludes the step of: coupling a dual mode display adapter to theexternal CRT for accepting the external video signal.
 14. The method ofclaim 13 wherein step (a) further includes the step of: coupling asecond multiplexer between the external CRT connector and adigital-analog-converter for isolating the output of thedigital-analog-converter so that the external video signal may bereceived through the dual mode display adapter and the external CRTconnector.
 15. A dual display mode portable computer comprising: aflat-panel display; a display controller for generating an internalvideo signal; and receiving means for receiving an external videosignal, the receiving means including, a dual mode display connector forreceiving the external video signal, an analog-to-digital convertercoupled to the dual mode display connector for converting the externalvideo signal into a digital external video signal, converter logiccoupled to the analog-to-digital converter for mapping the digitalexternal video signal into a format required by the flat-panel, and amultiplexer coupled to the display controller and the converter logicfor receiving the internal video signal and the external video signal,such that that in a first display mode, the multiplexer outputs theinternal video signal to the flat-panel display, while in a seconddisplay mode, the multiplexer outputs the external video signal to theflat-panel display, thereby enabling the portable computer to act as adisplay device for an external computer.
 16. A dual display modeportable computer comprising: a flat-panel display; a display controllerfor generating an internal video signal; a digital-to-analog converterand an external CRT connector for outputting the internal video signalto an external monitor; and receiving means for receiving an externalvideo signal, the receiving means including, a dual mode display adaptercoupled to the external CRT connector for enabling the external CRTconnector to receive an external video signal, an analog-to-digitalconverter coupled to the external CRT connector for converting theexternal video signal into a digital external video signal, converterlogic coupled to the analog-to-digital converter for mapping the digitalexternal video signal into a format required by the flat-panel; a firstmultiplexer coupled between the digital-to-analog converter and theexternal CRT connector, and a second multiplexer coupled to the displaycontroller and the converter logic for receiving the internal videosignal and the external video signal, such that in a first display mode,the first multiplexer outputs the internal video signal to theflat-panel display, while in a second display mode, the firstmultiplexer isolates output from the digital-to-analog converter whilethe second multiplexer outputs the external video signal to theflat-panel display, thereby enabling the portable computer to act as adisplay device for an external computer.